I have this pitts style Bisson muffler. http://www3.towerhobbies.com/cgi-bin...?&I=LX8680&P=0
The pressure fitting points at the fire wall. I can install the fuel tubing vent line, but it has a pretty tight turn and might rub against the firewall. Can someone please tell me where I can get a 90 degree fitting to replace the straight one that comes with the muffler?
Thanks for your help.

If it happens that you could not find any 90o fitting (personally I have not seen any), then you could carve into the firewall to make room for the line, after carving you will need to seal the wood with epoxy or any other wood sealer, so the fuel could not penetrate the wood.

I agree. Just carve out the wood in the firewall in order to give you enough room to make your connection. As was said above, make sure to re-seal the wood when you are done.

Ken

Or drill and tap the muffler to move the nipple elsewhere.

I thought about just drilling two holes in the firewall and run the tubing from the muffler, in and back out of the firewall, and to the vent line on the tank. Does that make sense?
Missleman,
Thought about drilling and tapping, but would have to buy the correct size tap (do you know what that is?) and a plug for the old hole.
I'll figure something out.
Thanks

Yes it makes sense, personally I do not like to make a bunch of holes in the firewall, because the oil tends to run inside the fuse easily but if it likes to be a good choice then you should go that way, just try to seal the better that you can.

Just out of curiosity, what model?

I use that muffler on a number of airplanes and none needed the engine mounted so close to the firewall that there was interference.

It's on the GP Venus 40 with an OS 55.
When I get home I will post some pictures, that is if my wife charged the camera battery[X(]

This part does'nt give the thread size, but you could give it a try, most of the ones that come with Perry pumps are 6-32.

http://www3.towerhobbies.com/cgi-bin...?&I=LXTT83&P=0

I ran a .46-AX in one of these but it was inverted with the stock muffler. You'll love he way that .55 sounds with the pitts.

Macs has some 90 degree fittings that might work: http://www.macspro.com/accessories.asp

After some years in the Hobby I had never used a 90o fitting, not because I do not like them, just because I have never seen them before, now that I am aware that they are so handy I would not hesitate on buy them and try them.

Good luck.

Hey guys, thanks for the info on the fittings. I got the vent line installed without rubbing on the firewall, it just make a little tighter bend that I wanted. I am going to buy some 90 degree fittings and see if I can get the right tap for them, just in case the vent line starts to slide off. Thanks again.